ZETA RET (Zeta Reticuli). For observers of the skies south of
about 35 degrees south latitude, the modern constellation of Reticulum (the Net) is circumpolar and
perpetually visible, its brightest star, Alpha Reticuli, shining at a modest third
magnitude. At the extreme western edge of the constellation lies
one of the few genuine naked-eye double stars, a two-for-one
combination named Zeta Reticuli. Separated by 310 seconds (a bit
over five minutes) of arc (0.09 degrees), the sixth magnitude
(5.54) western one (Zeta-1) keeps exact pace with the somewhat
brighter fifth magnitude (5,24) eastern component (Zeta-2), showing
that they are a real gravitational pair (but so far apart that no
orbit is detectable). In that sense it is a fine southern
hemisphere counterpart to the Big
Dipper's Mizar and Alcor and to Epsilon
Lyrae. Unlike these, however, it is a quite-remarkable pairing
of two SOLAR type stars, Zeta-1 listed as a G3-5 dwarf, Zeta-2 as
very-solar G2. (The classification is uncertain, Zeta-1 sometimes
given as G2, Zeta-2 as G0). Close to us, the Zeta-pair is only
39.5 light years away. From that and a temperature of 5795 Kelvin,
Zeta-2 shines with luminosity almost exactly the solar luminosity,
while Zeta-1 (at 5675 Kelvin) comes in at 0.9 Suns, which yield respective radii of 0.9 and
1.0 times solar and subsolar masses of 0.9 and 0.96 solar masses.
Given the angular separation and distance, the two are at least
3750 Astronomical Units apart, which with the total system mass of
1.86 solar, gives an orbital period of at least 170,000 years. As
if a solar-type double is not enough, what truly sets these stars
apart is a bizarre story of an alien abduction in the early 1960s
in which one of the abductees spotted a map in the alien spaceship
that was later traced back to the home base of Zeta Reticuli!
Which of the two stars was not said. Seems unlikely. And it's
even more unlikely, since no planets have yet been discovered
(though Earth-like ones would be undetectable). Moreover, stars
with planets tend to be metal-rich, whereas Zeta Ret is mildly
metal deficient, with an iron abundance about 60 percent solar,
consistent with a relatively high velocity compared to the Sun
(about five times normal). Too bad, as any residents of either
Zeta-1 or Zeta-2 could in principle travel back and forth from one
star to the other (real star travel being unlikely outside of such
pairs). From either, the other would be brilliantly obvious,
shining roughly as brightly as 30 times our Venus does in Earthly
skies, about the same as a mid-crescent Moon. (Thanks to Jerry
Diekmann and Tim De Benedictis who suggested this star.)